JPH0711341A - Method and device for controlling crown of hearth roll in continuous heat treatment furnace - Google Patents

Abstract

PURPOSE:To appropriately keep the roll crown during operating by arranging a core in the inner part of a hollow hearth roll, flowing coolant into gap between the core and a roll shell and executing the control-cooling. CONSTITUTION:In the case of being the band steel temp. at the inlet side of a heating zone lower than the atmospheric temp., in the inner part of the hearth roll 1, the cores 3 having the gaps with the inner surface of the roll shell are arranged at the two positions coming into contact with each of the edges of the band steel S. The core 3 has a cylindrical shape and a constitution connecting to a coolant supplying tube 4 for feeding the coolant from a coolant supplying device 11 with the inner peripheral surface and discharging the coolant from a coolant discharging hole 9. In the case of varying the temp. distribution of the roll shell 2 by changing the operational condition, based on information of temp. sensors 7a-c, the coolant supplying quantity is controlled with an arithmetic command device 12 to keep the roll crown to the appropriate range. Further, in the case of being the band steel temp. at the inlet side of a cooling zone, the core 3 is made to be the type integrated to the one body to cool the part of the roll shell 2 coming into contact with the center part of the band steel S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crown control method and control device for a hearth roll when a strip such as a steel strip is continuously passed through a heating furnace to perform heat treatment such as annealing. is there.

[0002]

2. Description of the Related Art When a strip such as a steel strip is passed through a continuous heat treatment furnace, the strip is supported by a hearth roll provided in the furnace and conveyed. At this time, the roll shell is provided with a crown so that the strip does not meander in the axial direction of the hearth roll. If the crown is small, the strip will meander, and it will be out of a predetermined position in the furnace and proper heat treatment cannot be performed, and it will cause troubles such as contact with the furnace wall. If the crown is too large, a wrinkle called a heat buckle occurs on the strip. Therefore, the crown of the roll shell must be maintained at a proper value at all times during operation.

By the way, when the set temperature of the heating furnace is changed, or the size (width, thickness) of the strip to be stripped and the stripping speed are changed even if the temperature is constant, the inlet side and outlet side of the heating zone and At a place where there is a large difference between the ambient temperature and the strip plate temperature, such as the cooling zone entrance side, the crown of the roll shell may change, and meandering or heat buckling may occur. That is, while the hearth roll temperature is the ambient temperature,
Since the strip plate temperature is lower than the ambient temperature on the heating strip entrance side, the portion of the roll shell 2 in contact with the strip plate S is cooled and contracted to reduce the crown, as shown in the partial sectional view of FIG. 6A. The strip plate S becomes easy to meander. Further, since the strip plate temperature is higher than the ambient temperature on the cooling zone entrance side, the portion of the roll shell 2 in contact with the strip plate S expands and the crown becomes large as shown in FIG. Buckles are likely to occur.

Conventionally, as a means for solving such a problem, the applicant of the present invention has proposed a control method of spraying a refrigerant whose temperature and flow rate are adjusted to the roll shell from inside or outside of the hollow hearth roll to maintain an appropriate crown. Japanese Patent Office Sho 5
No. 8-43454. Further, as a method of cooling from the inside of the hollow hearth roll, Japanese Patent Laid-Open No. 58-58-
56826 and JP-A-4-202716,
External cooling methods include JP-A-62-253734 and JP-A-63-38532. However, each of these internal cooling methods has a complicated structure, and the one that blows the cooling gas to the inner surface of the roll shell using a nozzle is
Since it is necessary to use a large number of nozzles in order to increase the response speed and to increase the discharge flow rate, the nozzle diameter is small, and troubles such as clogging are likely to occur, resulting in a heavy maintenance burden. In addition, these external cooling methods have a problem that the response is inferior because only a part of the roll circumferential direction is cooled because it is necessary to install so as not to interfere with the strip, and the cooling capacity is increased to improve the response. If this happens, the pressure inside the furnace may fluctuate and the temperature of the furnace may drop, which may lead to mixing of outside air and deterioration of thermal efficiency. Further, the applicant of the present invention has disclosed that a roll shell made of heat-resistant steel is provided with a layer of a metal having a large thermal conductivity in a layered manner to make the temperature distribution in the roll axial direction uniform and maintain an appropriate crown. No. 163326, but no sufficient effect has been obtained. Further, according to Japanese Patent Laid-Open No. 4-131328, a plurality of slits continuous in the axial direction and penetrating the hollow portion are provided on the outer periphery of the roll shell to prevent the fluctuation of the crown by absorbing the strain in the roll circumferential direction. Although proposed, there is a problem that the sprayed film is easily peeled off when the roll surface is coated with the sprayed film.

[0005]

DISCLOSURE OF THE INVENTION The present invention, in a continuous heat treatment furnace for strips such as steel strips, prevents the strips from meandering or heat buckling even if the strip size or operating conditions are changed. The purpose of the present invention is to provide a technique for constantly maintaining the crown of the hearth roll in an appropriate range during operation and controlling the crown amount with a simple structure and high responsiveness.

[0006]

According to the present invention, a hollow core is provided inside a hollow hearth roll in a continuous heat treatment furnace for strips, and a core is partially provided in the roll axial direction with a gap between the hollow hearth roll and the inner surface of the roll shell. A crown control method and a control device for a hearth roll, characterized by cooling the roll shell at the portion where the core is disposed by passing a refrigerant through the gap,
The temperature distribution of the roll shell is measured as necessary, and the supply amount of the refrigerant is adjusted based on the measured temperature distribution.

FIG. 1 shows a vertical cross section of a hearth roll and a control system according to the present invention. The temperature of the strip is lower than the ambient temperature, such as the heating zone entrance side of a continuous heat treatment furnace, and the hearth roll is cooled by the strip. It is an application example in the case of being performed. Inside the hollow hearth roll 1, cores 3 are provided at two positions in the roll axial direction with a gap from the inner surface of the roll shell 2. At that position, the edge of the strip S is the roll shell 2
It is the part that touches. The core 3 has a cylindrical shape, and a coolant supply pipe 4 is connected to the inner peripheral surface thereof, and the axes thereof coincide with the axis of the roll shell 2. The refrigerant supply pipe 4 is joined to the roll shell 2 at the end of the roll shell 2, and the rotary joint 6 is provided outside thereof.
Communicates with the refrigerant inlet 8. Reference numeral 5 is a bearing at the connection portion with the furnace wall of the continuous heat treatment furnace. The coolant is supplied from the coolant supply device 11 to the coolant introduction port 8, and the coolant passes through the coolant supply pipe 4 and the inner peripheral surface of the core 3 as shown by an arrow to form the roll shell 2 and the core 3. It is discharged from the refrigerant discharge port 9 through the gap. When the coolant is circulated and used, the coolant discharge port 9 is provided in the rotary joint 6, and heat is exchanged to guide it to the coolant supply device 11. As the refrigerant, a gas such as air, nitrogen, or argon, or a mist composed of these gases and water can be used.

FIG. 2 also shows a vertical section and control system of the hearth roll according to the present invention. The temperature of the strip plate is higher than the ambient temperature and the hearth roll is heated by the strip plate, such as the cooling zone entrance side of the continuous heat treatment furnace. It is an application example in the case of being performed. Core 3
Is provided at one site where the strip plate S is in contact with the roll shell 2, and a slit 10 is provided at the center. As shown by the arrow, the coolant is supplied from the coolant supply pipe 4 into the core 3, passes through the gap between the roll shell 2 and the core 3, and is discharged from the coolant discharge port 9.

In the example of FIGS. 1 and 2, when the operating conditions such as the size of the strip S, the strip passing speed, and the furnace temperature are constant, and the temperature distribution of the roll shell 2 is constant, the supply amount of the refrigerant is constant. However, if the temperature distribution of the roll shell 2 changes, such as when the operating conditions change or the size of the strip S changes, for example, the temperature sensors 7a, 7
The supply amount of the refrigerant is adjusted by the temperature distribution based on the information from b and 7c. Reference numeral 12 is a calculation command device that calculates a refrigerant supply amount required to maintain the crown of the roll shell 2 in an appropriate range based on information from each temperature sensor 7 and issues a command to the refrigerant supply device 11. The temperature sensor 7 is detached from the portion where the core 3 of the roll shell 2 is provided, the portion contacting the central portion of the strip S in the example of FIG. 1, and both edges of the strip S in the example of FIG. 2 to the outside. It is only necessary to input temperature information such as parts and the like to the operation command device 12, and a pyrometer that gazes at the outer peripheral surface of the roll shell 2 or a transmission type that is embedded in the roll shell 2 can be used.

In the present invention, the refrigerant passes through the narrow gap between the core 3 inside the hollow hearth roll 1 and the roll shell 2 at a high speed, and at this time, the roll shell 2 at the portion where the core 3 is provided is It is cooled efficiently in the circumferential direction. Figure 1
In the example, the portion of the roll shell 2 in contact with the strip plate S is cooled by the strip plate S and shrinks to try to reduce the crown, but due to the cooling effect of the refrigerant passing through the gap between the roll shell 2 and the core 3. Since both edge portions of the strip S and parts outside both edges also contract, an appropriate crown can be maintained. In the example of FIG. 2, the portion of the roll shell 2 in contact with the strip plate S is heated by the strip plate S and expands to increase the crown, but due to the refrigerant passing through the gap between the roll shell 2 and the core 3. Due to the cooling effect, heat expansion is suppressed, and a proper crown can be maintained. In both cases, the cooling effect of the roll shell 2 depends on the material and size of the roll shell 2 and the core 3.
Shape, gap between roll shell 2 and core 3, strip material / dimension / passing speed, atmosphere / temperature of heat treatment furnace, type of refrigerant,
Although it varies depending on factors such as the supply amount of the refrigerant, during the operation in which the same hollow hearth roll is used in the same furnace, the temperature distribution of the roll shell 2 is controlled by adjusting the supply amount of the refrigerant, and the crown is controlled. Control can be performed. As the refrigerant, gas or mist can be used as described above, but liquid is not preferable because it causes slip flaws during acceleration / deceleration due to a large increase in roll inertia.

Regarding the axial length and arrangement position of the core 3 in the present invention, preferable ranges for maintaining an appropriate crown of the roll shell are as follows. When passing a strip plate having a temperature lower than the ambient temperature of the hollow hearth roll, as shown in FIG. 1, the core 3 is arranged at two portions where both edges of the strip S are in contact with the roll shell. The axial length and arrangement of the core 3 are set so that the distance between the cores 3 is 50% or more of the width of the band S and the edges of the band S are 100 mm or more away from both ends of the core 3. It is preferable to determine the installation position. When the strip plate having a temperature higher than the ambient temperature of the hollow hearth roll is passed, the core 3 is disposed at one central portion of the strip S as shown in FIG. 2, and the axial length of the core 3 is set. Is preferably 30% or more of the plate width of the strip S and the edge of the strip S is projected 100 mm or more outward from the end of the core 3. Further, the gap between the roll shell 2 and the core 3 is preferably in the range of 1 to 5 mm in view of manufacturability and cooling ability.

Next, a specific example in which the temperature distribution of the roll shell is measured in accordance with a command from the operation command device 12 and the refrigerant supply amount is calculated to perform crown control will be described with reference to the flow chart of FIG. 1 and 2, the temperature sensors 7a, 7
b. The temperature T ₁ , T ₂ , T ₃ of the roll shell 2 by 7c
Is calculated, and the crown amount δ is calculated by the equation (1). δ = {T ₂ −1/2 (T ₁ + T ₃ )} αR + δ _i (1) The calculation result is compared with the target crown amount δ _o, and when δ = δ _o , the refrigerant supply amount does not change, δ <δ _{o Alternatively} , when δ> δ _o, the required temperature drop amount ΔT is calculated by the equation (2) in the case of the edge cooling, and the required refrigerant supply amount Q is calculated by the equation (3) in the case of the central portion cooling. ΔT = (δ _o −δ) / αR + ΔT _i (2) ΔT = (δ−δ _o ) / αR + ΔT _i (3) Q = A {KΔT / (T−ΔT−Tg)} ^1.25 (4) T = 1 / 2 (T ₁ + T ₃ ) with edge cooling (5) T = T _{2 with} center cooling (6) δ: Crown amount δ _i : Initial crown amount δ _o : Target crown amount α: Roll shell line Expansion ratio R: Roll shell radius ΔT: Required temperature drop ΔT _i : Initial temperature drop Q: Required refrigerant supply A: Gap cross-sectional area between roll shell and core K: Coefficient determined by low shell size and furnace conditions Tg: Cooling gas temperature Temperature sensors 7a, 7b. 7c, the temperatures T ₁ , T ₂ , T ₃ of the roll shell 2 are measured, and the crown amount δ is calculated by the equation (1).

[0013]

【Example】

(Invention Example 1) Diameter D = 800 mm as shown in FIG.
In a heat-resistant stainless steel roll shell 2 having a body length L = 2000 mm and a shell thickness of 25 mm, two heat-resistant stainless steel cores 3 having a length a = 400 mm, a mutual distance d = 1200 mm,
A hollow hearth roll provided with a gap of 3 mm from the inner surface of the roll shell was used to set the atmosphere temperature on the heating zone inlet side of the steel strip continuous annealing furnace to 9
It is installed at the position of 00 ℃, and the steel strip with width W = 1600mm is 25
The plate was annealed by passing it at a speed of 0 m / min. As a result of measuring the temperature of the roll shell 2 with an embedded thermocouple, T ₁ = 370 ° C., T
₂ = 200 ° C., T ₃ = 330 ° C., and the calculation result of the crown amount by the equation (1) was δ = 1.64 mm. The initial crown amount was δ _i = 3 mm. Since δ <δ _o was compared with the target crown amount δ _o = 2 mm, the supply amount of air at 50 ° C. as a refrigerant was calculated. Required temperature drop Δ
T becomes ΔT = 53 ° C. according to the equation (2), and the refrigerant supply amount Q
From the equation (4), Q = 3.5 m ³ / min. When this amount of refrigerant was supplied, the crown amount δ almost coincided with the target crown amount δ _o = 2 mm.

(Invention Example 2) Diameter D as shown in FIG.
= 700 mm, body length L = 1800 mm, shell thickness 25 mm, inside heat-resistant stainless steel roll shell 2, length b = 800
mm heat-resistant stainless steel core 3 and a hollow hearth roll provided at the center with a gap of 2 mm from the inner surface of the roll shell.
Installed at the position of 300m /
The plate was passed at a speed of minutes and cooled. As a result of measuring the temperature of the roll shell 2 with an embedded thermocouple, T ₁ = 180 ° C., T ₂ = 4
The temperature was 50 ° C. and T ₃ = 220 ° C., and the calculation result of the crown amount by the formula (1) was δ = 2.49 mm. The initial crown amount was δ _i = 1 mm. Target crown amount δ _o =
Compared to 2 mm, δ> δ _o , so 50 as a refrigerant
The amount of air supply at ° C was calculated. The required temperature drop amount ΔT was ΔT = 82 ° C. according to the formula (3), and the refrigerant supply amount Q was Q = 13 m ³ / min according to the formula (4). When this amount of refrigerant is supplied, the crown amount δ becomes the target crown amount δ _o.
= 2 mm, which is almost the same.

[0015]

According to the present invention, in a continuous heat treatment furnace for strips such as steel strips, even if the strip size or operating conditions are changed or fluctuated, the hearth roll crown is always kept in an appropriate range during operation. It is maintained and the meandering of the strip and the heat buckle are prevented. In the present invention, it is possible to perform control with good responsiveness in a simple structure without providing a cooling nozzle in the hollow hearth roll as in the conventional case.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a cross section of a hearth roll and a control system in the present invention.

FIG. 2 is a diagram showing another example of a cross section of a hearth roll and a control system according to the present invention.

FIG. 3 is a diagram showing an example of a control system in the present invention.

FIG. 4 is a partial sectional view showing an embodiment of the present invention.

FIG. 5 is a partial cross-sectional view showing an embodiment of the present invention.

FIG. 6 is a partial cross-sectional view showing a conventional hearth roll.

[Explanation of symbols]

1: Hollow hearth roll 2: Roll shell 3: Core 4: Refrigerant supply pipe 5: Bearing 6: Rotating joint 7a, 7b, 7c: Temperature sensor 8: Refrigerant inlet 9: Refrigerant outlet 10: Slit 11: Refrigerant supply Device 12: Calculation command device S: Strip plate D: Roll shell diameter L: Roll shell body length T ₁ , T ₂ , T ₃ : Roll shell temperature W: Strip plate width a, b: Core length d: Core Interval between

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroo Ishibashi 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Stock of Kimitsu Steel Co., Ltd.

Claims (4)

[Claims] 1. A hollow hearth roll in a continuous heat treatment furnace for a strip is provided with a core partially in the roll axial direction with a gap between the hollow hearth roll and the inner surface of the roll shell, and a refrigerant is passed through the gap. A method for controlling crown of a hearth roll in a continuous heat treatment furnace, comprising: 2. The method for controlling a crown of a hearth roll according to claim 1, wherein the supply amount of the refrigerant is adjusted based on the temperature distribution of the roll shell. 3. A core, which is partially provided in the roll axial direction with a gap between it and the inner surface of the roll shell of the hollow hearth roll provided in the continuous heat treatment furnace for the strip, and a coolant is supplied to the gap. A crown control device for a hearth roll in a continuous heat treatment furnace, comprising: 4. A temperature sensor for detecting temperatures at a plurality of positions in the axial direction of the roll shell, and a calculation command device for calculating a supply amount of the refrigerant based on information from the sensor and issuing a command to the refrigerant supply device. A crown control device for a hearth roll in a continuous heat treatment furnace according to claim 3.